The present invention generally relates to solar powered electric generating systems and more particularly to a device and method for controlling a flux input to a solar receiver.
Solar dishes that are formed from a plurality of reflective solar panels are commonly employed for concentrating solar energy and directing this energy to a power conversion unit that converts the solar energy into mechanical and/or electrical energy. A typical power conversion unit has a solar receiver which is positioned relative to the solar dish so as to receive the concentrated solar energy reflected by the solar panels. During the operation of the power conversion unit, it is highly desirable that an even flux be maintained on the receiver so as to increase its service life and ensure efficient operation. Variances in the flux transmitted to the receiver are relatively common and generally result from tracking variation and reflective surface variation. Tracking variation is associated with the positioning of the solar dish and generally results from the control interval that is employed to periodically reposition the solar dish, axis tilts, winds, gravity bending, mirror soiling and track errors. Reflective surface variation is associated with the concentrated light that is reflected by the solar panels and generally results from surface waviness, variation in the radius of curvature and the alignment of the facets (solar panels).
The application of an uneven flux to a power conversion unit results in higher temperature differentials on the receiver and an uneven power distribution among the sectors of the receiver. Uneven power distribution tends to reduce the efficiency and service life of the power conversion unit. Higher temperature differentials tend to increase the thermal stress on the receiver, thereby reducing its operating life as well as the efficiency with which it operates. Since the receiver is an expensive component, the decreased life undesirably increases the operating costs of the power conversion unit. Accordingly, a system and method for reducing flux variation is therefore desired.
In one preferred form, the present invention provides a solar power system including a mirror that is configured to receive and concentrate solar energy, a mirror positioning mechanism, a receiver, a plurality of sensors and a controller. The mirror positioning mechanism is coupled to the mirror and is configured to adjust a position of the mirror. The receiver is coupled to the mirror and is configured to receive the concentrated solar energy from the mirror. The receiver is divided into a plurality of sectors, with each of the sectors receiving a portion of the concentrated solar energy. Each of the sensors is coupled to an associated one of the sectors and is operable for generating a sensor signal indicative of an amount of energy transmitted into the associated one of the sectors. The controller is coupled to the mirror positioning mechanism and the sensors. In response to the receipt of the sensor signals, the controller determines a differential indicative of a difference in a flow of energy into the sectors and controls the mirror positioning mechanism in response to the differential to affect the concentrated solar energy that is transmitted into the receiver and maintain the differential below a predetermined differential limit.
In another preferred form, the present invention provides a method for positioning a solar concentrator. The method includes the steps of providing a receiver having a plurality of sectors, each of the sectors being operable for converting concentrated light energy into a second form of energy; positioning the solar concentrator to reflect concentrated light energy onto the sectors; monitoring a flow of energy transmitted into each of the sectors; calculating a differential indicative of a difference in the energy flows into the sectors; and repositioning the solar concentrator to maintain the differential below a predetermined differential limit.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.